Re: [PATCH 4/9] drm/connector: Add support for out-of-band hotplug notification

[Imre Deak <imre.deak@intel.com>]

On Mon, May 03, 2021 at 11:00:20AM +0300, Heikki Krogerus wrote:
> Hi Hans,
> 
> On Wed, Apr 28, 2021 at 11:52:52PM +0200, Hans de Goede wrote:
> > +/**
> > + * struct drm_connector_oob_hotplug_event_data: OOB hotplug event data
> > + *
> > + * Contains data about out-of-band hotplug events, signalled through
> > + * drm_connector_oob_hotplug_event().
> > + */
> > +struct drm_connector_oob_hotplug_event_data {
> > +	/**
> > +	 * @connected: New connected status for the connector.
> > +	 */
> > +	bool connected;
> > +	/**
> > +	 * @dp_lanes: Number of available displayport lanes, 0 if unknown.
> > +	 */
> > +	int dp_lanes;
> > +	/**
> > +	 * @orientation: Connector orientation.
> > +	 */
> > +	enum typec_orientation orientation;
> > +};
> 
> I don't think the orientation is relevant. It will always be "normal"
> from DP PoW after muxing, no?
> 
> I'm also not sure those deatils are enough in the long run. Based on
> what I've understood from our graphics team guys, for example knowing
> if multi-function is preferred may be important in some cases.

Combo PHY ports - which is what this patchset is adding the notification
for - can only reverse the lane assignment. TypeC PHY ports (on ICL+)
have a more C-type aware mux in the SoC (FIA) as well, so in theory we
could have a system based on such platforms with an external mux only
switching between the USB, DP, USB+DP (MFD) modes, but leaving the plug
orientation specific muxing up to the FIA. The graphics driver is not
involved in programming the FIA though, it's done by a firmware
component, so I don't think this configuration needs to get passed.

Yes, the driver needs to know if the PD controller configured the sink
in the MFD mode (DP+USB) or in the DP-only mode. For that the number of
lanes assigned to DP is enough.

> +Imre.
> 
> All of that, and more, is already available in the Configuration VDO
> Status VDO that the we have negotiated with the DP partner. Both those
> VDOs are part of struct typec_displayport_data. I think we should
> simply supply that structure to the DRM code instead of picking those
> details out of it...
> 
> >  /**
> >   * struct drm_tv_connector_state - TV connector related states
> >   * @subconnector: selected subconnector
> > @@ -1110,6 +1132,15 @@ struct drm_connector_funcs {
> >  	 */
> >  	void (*atomic_print_state)(struct drm_printer *p,
> >  				   const struct drm_connector_state *state);
> > +
> > +	/**
> > +	 * @oob_hotplug_event:
> > +	 *
> > +	 * This will get called when a hotplug-event for a drm-connector
> > +	 * has been received from a source outside the display driver / device.
> > +	 */
> > +	void (*oob_hotplug_event)(struct drm_connector *connector,
> > +				  struct drm_connector_oob_hotplug_event_data *data);
> 
> So I would not try to generalise this like that. This callback should
> be USB Type-C DP altmode specific:
> 
> 	void (*oob_hotplug_event)(struct drm_connector *connector,
>                                   struct typec_displayport_data *data);
> 
> Or like this if the orientation can really be reversed after muxing:
> 
> 	void (*oob_hotplug_event)(struct drm_connector *connector,
> 				  struct typec_altmode *altmode,
>                                   struct typec_displayport_data *data);
> 
> You can now check the orientation separately with
> typec_altmode_get_orientation() if necessary.
> 
> 
> thanks,
> 
> -- 
> heikki